Stop Using SSH | ~andersonvom

Stop Using SSH 01 Sep 2014

Actually, don’t do that quite yet, but be aware of an interesting alternative that may come in handy a lot of times, especially when your connection is flaky and unreliable. When SSHing into a remote machine, things will be just fine as long as your connection is snappy and you’re not getting too much output from the server. Once you get disconnected from your VPN, you move between networks (WiFi or mobile), you start lagging behind due to network usage/issues, or you get A LOT of output from your remote server, SSH just doesn’t respond properly.

Mosh (short for Mobile Shell) is a remote terminal application that is bootstrapped on SSH but runs standalone afterwards to try and solve the problems listed above. It will SSH into the remote machine and start a UPD connection between your local and remote server. From this point on, it will try to keep your current screen in sync, without caring too much about lost packages or text that is long gone in your scroll. It will also try to predict your local echo, so that you see what you’re typing without having to wait for the request to go to the remote server and back.

Installation

This is the hard part:

sudo apt-get install mosh  # Debian-based distros
brew install mobile-shell  # Mac

If you use a different system, see more info here. Moving on…

Usage

Using it is pretty straightforward and very similar to SSH:

# This will connect to example.com as user on port 22
mosh [user@]example.com

… but not without its caveats:

# Depending on how you install it, you may have to specify the server path
# I'm having this problem when connecting to Macs
mosh --server=/usr/local/bin/mosh-server example.com

# If you want to connect to a different SSH port, -p is not the option
# It changes the UDP post for mosh, instead you'll use:
mosh --ssh="ssh -p 2222" example.com

Issues

This are still evolving and there are some annoying things that still happen when using Mosh.

You will lose your scroll: this should be solved in Mosh 1.3, but for now, you won’t be able to scroll up unless you’re using tmux/screen in the remote server as well.
You have to have more open ports: unfortunately Mosh connects via UDP on ports 60000+, so you have to have these ports open as well as SSH port on your remote server.